Pseudomonas aeruginosa is obligately aerobic gram negative bacillus being widely existing in the natural world. Although its pathogenicity is usually low, it is a pathogen that causes opportunistic infections often occurring in patients suffering from various pre-existing diseases such as cancer and diabetes, and in patients administered with pharmaceuticals having immune-inhibitory action, and may often cause pneumonia, urinary tract infection, sepsis and the like to lead to severe results. In clinical fields, pseudomonas aeruginosa infection is considered as one of the most difficult infections to be treated because not only Pseudomonas aeruginosa has inherently low sensitivity to existent antibiotics, but also has high tendency to easily acquire resistance to various antibiotics and to become difficult to cure. Thus for Pseudomonas aeruginosa, the measure of developing new antibiotics one after another is limited, and a therapeutic method that does not rely on antibiotics is strongly desired.
High cytotoxicity of Pseudomonas aeruginosa is exerted by injection of toxin into a eukaryotic cell via a type III exotoxin secretion system. PcrV is a protein of 294 residues (NCBI Accession No. AAC45935, SEQ NO: 1) constituting the type III exotoxin secretion system, and an operon sequence encoding the same is open to the public (Patent document 1, Non-patent document 1). Since control for PcrV can possibly lead a therapeutic means in pseudomonas aeruginosa infection (Non-patent document 2), polyclonal antibodies (Non-patent documents 3, 4) and monoclonal antibodies (Patent document 2, Non-patent documents 5, 6) against PcrV having neutralizing activity are reported. However, polyclonal antibodies are difficult to be humanized and to be used as pharmaceutical compositions because of difficulty in improvement of antigenicity. Also the monoclonal antibodies having reported heretofore have low neutralizing activity and fail to satisfy requirements in clinical fields.    Patent document 1: U.S. Pat. No. 6,551,795    Patent document 2: Japanese Translation of PCT publication No. 2005-500250    Non-patent document 1: Yahr, T. L. et al., J. Bacteriol., 1997, vol. 179, p. 7165    Non-patent document 2: T. Sawa et al., Nature Medicine, 1999, vol. 5, p. 392    Non-patent document 3: Shime N et al., J. Immunol. 2001, vol. 167, p. 5880    Non-patent document 4: Imamura Y et al., Eur. Respir. J., 2007, Vol. 29, p. 965    Non-patent document 5: Karine Faure et al., J. Immune. Based. Therapies and Vaccines, 2003, Vol. 1    Non-patent document 6: Dara W. Frank et al., J. Infect. Disease, 2002, Vol. 186, p. 64